Tente isto:
Boot
de um Ubuntu Live USB
com uma conexão ativa com a Internet.
Open
a Janela do terminal (Applications ---- Accessories ---- Terminal)
.
Type
do seguinte commands
:
sudo -i
apt-get update
apt-get install cryptsetup lvm2
fdisk -l
cryptsetup luksOpen /dev/sda? TAG #sda? is your root partition
vgchange -ay
vgscan
vgchange -ay [VOLUME GROUP NAME]
lvscan
/dev/[VOLUME GROUP NAME]/[LOGICAL VOLUME NAME] /mnt
modprobe efivars
mount /dev/sda? /mnt/boot/efi #sda? is your efi partition
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
cp /etc/resolv.conf /mnt/etc/
chroot /mnt
apt-get install --reinstall grub-efi-amd64
or
apt-get install --reinstall grub-efi
update-grub
umount /mnt
vgchange -an
cryptsetup luksClose TAG